The invention relates to a method for preparation of a fresh, cold, coffee-based beverage, using a predetermined amount of coffee grounds. The invention furthermore relates to a corresponding, fully automatic, coffee machine which may be of the piston-type. Fresh coffee-based beverages can be produced in the standard way, for example with a filter coffee machine. In addition, fresh coffee-based beverages can also be prepared with the aid of piston-type machines (so-called specialty machines). Insulated containers with a corresponding warming unit are necessary to keep larger amounts of filtered coffee ready for use.
Piston-type machines produce coffee-based beverages with a high share of turbid and suspended materials, which are not desirable for a typical filtered coffee. The reason for this is that piston-type machines push the complete beverage amount with high pressure through a brewing unit, wherein a small amount of hot water, which is clearly lower than the amount guided through the brewing unit, is added later on if necessary, for example via a bypass line. The turbid and suspended materials dissolved out of the coffee grounds during this process then enter the beverage ready for drinking. These turbid and suspended materials, however, are desired for products prepared with a piston-type machine, for example for espresso and Schümli products (wherein beans by Julia Schümli are especially desired for these products). For that reason, these types of machines could not, so far, be used for the preparation of products similar to filtered coffee.
German patent document DE 44 09 030 C2 describes a method for the production of a coffee-based beverage, as well as a suitable coffee machine provided with a bypass. The coffee-based beverage is prepared using a predetermined amount of ground coffee and a coordinated amount of hot water, wherein only a portion of the hot water is guided through the coffee grounds for the extraction and then flows into a storage container. The remaining partial amount bypasses the coffee grounds and flows directly into the storage container. The amount flowing through the bypass line is controlled such that at all times a drinkable coffee quality exists inside the storage container. An attempt is made with this method to compensate for fluctuations in the coffee strength during the brewing process.
One known option for preparing a cold coffee-based beverage is the preparation of a specialty coffee, preferably an espresso, with the aid of a piston-type machine and subsequently pouring it over ice cubes. This type of preparation is characterized by the combination of ice cubes with a smaller amount of coffee, wherein the special drinking experience above all is based on the existing, non-melted ice.
With a different method for preparing a cold coffee-based beverage, for example, regular filtered coffee is produced with a filter coffee machine and is then filled into containers in which it is allowed to cool down to room temperature over a longer period of time. The coffee cooled down in this way is then removed from the containers and, if applicable, is served while filled with ice. These types of beverages, however, are no longer fresh at the time when they are dispensed because of the relatively long cooling down period.
The aforementioned method furthermore requires the storage of large amounts of brewed filter coffee since the cooling down period is relatively long, wherein furthermore cooling agents for keeping the beverage cool can require additional energy.